1. Field of the Invention
The present invention relates to optical tagging, tracking, and locating, and, more specifically, to optical tagging, tracking, and locating at significant distances.
2. Description of the Related Art
Long distance tagging, tracking, and locating (“TT&L”) is a major challenge. Current TT&L capabilities most often use radio frequencies (“RF”) to find their targets. This is becoming increasingly challenging in an RF jammed environment. Additionally, active RF emitters require a power source limiting their lifetime and range. Passive RF tags must be probed by an active source which can be readily detected and jammed. Current optical techniques are limited due to several problems. Most detection systems work in the visible or near-IR wavelengths. While this can have some advantages, such as near-IR's ability to cut through obscurants, it is very challenging to detect these wavelengths in daylight conditions due to the high background signal of ambient light. Significant polarization and grating of the light is required to detect any signal over the background. This process discards most of the emission signal and therefore has a very difficult time detecting signals at a significant distance.
The current optical emitters also suffer from inherent difficulties in the environment. Quantum dots, which have become quite popular, suffer from “blinking” as they get caught in their triplet state and electrons are unable to relax back down to the ground state. This makes pulsed detection and emission gating very difficult. UV-C quantum dots, which would at least solve the “solar-blind” problem, are also not available as no quantum dot has been synthesized to emit in the UV-C region. Organic fluorophores, which are an alternative to quantum dots, are susceptible to photobleaching and their optical performance is highly dependent on their local environment and solvation state. Finally, systems which simply functionalize quantum dots or fluorophore labeled particles do not emit the needed amount of light for long distance detection because of significant scattering effects. Light is not efficiently harvested and transferred to its emitting fluorophore, and particle composition and structure is not optimized to enhance photonic emission for detection. These combined optical inefficiencies make it extremely difficult if not impossible to perform optical tagging and tracking at significant distances.
Innovative technologies are therefore required for optical tagging, tracking, and locating at significant distances that avoid one or more problems currently faced by the state-of-the-art in TT&L capabilities.